Many types of ratchet wrenches are known in the art. One known type includes a wrench body, a ratchet gear having a plurality of gear teeth radially arranged on an outer peripheral surface thereof, and a spring loaded pawl having a set of gear engaging teeth. The pawl is generally received in a slot of the wrench body with the pawl being slidable within the slot. The spring urges the pawl into engagement with the ratchet gear such that the teeth thereof engage the ratchet gear teeth. As the wrench body is manually moved in a direction to apply torque to a fastener, the pawl teeth engage the gear teeth so that movement of the wrench body is applied as torque to the ratchet gear, which in turn is transmitted to the fastener As the wrench body is moved in the opposite direction, the pawl teeth disengage from and ride over the gear teeth against the biasing of the spring in a ratcheting manner. Examples of such wrenches are disclosed in U.S. Pat. Nos. 3,186,265 and 3,838,614.
One shortcoming of these types of wrenches is that when applying torque, the engagement between the gear engagement teeth of the pawl and the ratchet gear teeth results in significant shearing forces being transmitted through the pawl. For example, in the '265 patent when torque is being applied to a fastener, a substantial amount of shear stress is generated within the pawl. Specifically, the forces applied between the pawl and the gear are at an angle with respect to the direction in which the pawl is supported, thereby tending to cantilever the pawl against its supporting surface and generating the shear stress. It is known that yielding occurs under shear at a lower value than under tension/compression. The maximum shear stress criterion says that the amount of stress required for yielding under shear is half the value required for yielding under tension/compression. As a result, the pawl must be made more robust to prevent such yield. Further, in the wrench of the '265 patent when torque is applied most of the force applied to the gear is applied to only one gear tooth. As a result, because the gear is a ring-type gear, the gear wall thickness must be increased to withstand having the force localized in one area in such a manner.
Consequently, there is a need for providing a ratchet wrench wherein the transferal of forces from the pawl to the gear is handled in a more effective manner so as to reduce the stresses in one or both of those components.